Theses and Dissertations from UMD

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New submissions to the thesis/dissertation collections are added automatically as they are received from the Graduate School. Currently, the Graduate School deposits all theses and dissertations from a given semester after the official graduation date. This means that there may be up to a 4 month delay in the appearance of a give thesis/dissertation in DRUM

More information is available at Theses and Dissertations at University of Maryland Libraries.

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2011 - 20142

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    Ultrasensitive CITP-MS based targeted proteomics technologies for protein identification and quantification
    (2014) Wang, Chenchen; Lee, Cheng S; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Mass Spectrometry (MS) based technologies have enabled efficient and comprehensive proteomic profiling for biomarker discovery. However, due to sample complexity and large concentration variation, the obtained data is usually biased to endogeneous high abundance proteins while the important disease-related information went missing. Targeted proteomics enables the delivery of precise and sensitive qualitative/quantitative data of interest to researchers by focusing analysis on a preselected population of cells or proteins. This project aims to develop targeted proteomic technologies through capillary isotachophoresis (CITP)-based technique which is capable of selectively enriching trace compounds for a further improved sensitivity in both discovery and validation studies. By employing tissue microdissection and a CITP-based multidimensional separation platform, homogeneous glioma cells were isolated from unwanted cells and analyzed in search of glioblastoma biomarker. Comparative proteomic profiling of pure tumor cells from different grades of infiltrative astrocytomas revealed disease specific protein expression variation among grades. Further validation using immunohistochemistry demonstrated consistent results. This targeted tissue analyzing platform provided a sensitive and confident methodology for biomarker discovery within minute amount of samples. With the demonstrated outstanding analyzing capacity on targeted biomarker discovery, we moved on to developing ultrasensitive targeted quantitation techniques. We demonstrated online coupling of transient-CITP/CZE (capillary zone electrophoresis) with selective reaction monitoring (SRM) MS for the first time via a sheathliquid interface for improved sensitivity and selectivity. Ultrasensitive targeted quantitation was achieved through the incorporation of the selective enrichment capability of CITP/CZE with SRM MS, giving a limit of quantitation (LOQ) of 50 pM with a total sample loading of 50 attomoles. In order to further improve the sensitivity, we developed a novel sheathless interface which enables increased loading capacity and nanoflow operation by assembling a large size separation capillary and a small size porous emitter. LOQ was improved 5 times comparing to using the first sheathliquid interface, giving a LOQ of 10 pM with a total sample loading of 25 attomoles. This novel interface optimally preserved the high resolution and efficiency of CITP/CZE while improving the limited sample loading capacity, demonstrating a powerful analytic platform for targeted proteomic quantitation and validation.
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    PROBING ATMOSPHERIC AEROSOL AND GAS PROPERTIES WITH PHOTOACOUSTIC SPECTROSCOPY
    (2011) Bueno, Pedro Antonio; Zachariah, Michael R; Dickerson, Russell R; Chemistry; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)
    Absorption by atmospheric aerosols is the wild card for global climate change. Issues regarding atmospheric gases and aerosols have been at the forefront and the work presented within is directed at those issues. Specifically, work has been performed in order to help understand the issue of absorption in the atmosphere and whether this contributes towards positive forcing or warming of the atmosphere. In the process of conducting this research a custom, first-principles photoacoustic spectrometer was improved, calibrated and used extensively in order to obtain knowledge of the interaction of light with atmospherically relevant gases and make the first measurements of absorbing aerosols. The absorption cross-section of uncoated and coated soot was measured and quantified and found to be consistent with other work where amplifications on the order of nearly 100% were observed with uncertainty levels much lower than previously reported. Soot was also found to be optically thin where the total mass of the soot contributes to the absorption. Consequential to the soot work, the photoacoustic spectrometer developed to measure the absorption was utilized as a high precision greenhouse gas sensor. The photoacoustic spectrometer was found to produce results on the absorption of CO2 to within 3% of the theoretically predicted line profile Moreover, the photoacoustic spectrometer was used to determine measurable coating thicknesses of less than 10 nanometers on 100 nm soot particles.